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Ch.1. The Environmental Isotopes

Ch.1. The Environmental Isotopes. What is isotopes? ISO (same) + TOPE (position) Elements having same no of proton (Z), but different no of neutron (N) The same elements with different masses (A) A Z E N ( 18 8 O 10 )  Or smiply A E ( 18 O) . Types of isotopes Stable Unstable

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Ch.1. The Environmental Isotopes

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  1. Ch.1. The Environmental Isotopes • What is isotopes? • ISO (same) + TOPE (position) • Elements having same no of proton (Z), but different no of neutron (N) • The same elements with different masses (A) • AZEN (188O10)  Or smiplyAE (18O) .

  2. Types of isotopes • Stable • Unstable • Radiogenic • Heavy • Light • Nontraditional stable • Isotones & isobars ?

  3. Plot of Z vs. N for nuclides up to tin (Z = 50) showing the’ stable valley’ of the nuclides. See Fig. 1-1 on p.3 From www.sprawls.org/ppmi2/RADIOTRANS/

  4. Magic number of neutron? (2, 8, 28, 50, 82, 126) • What is environmental isotopes? • The isotopes used in the environmental studies (in the text, especially for the environmental hydrogeological studies)

  5. Significance of environmental isotopes (in hydrogeology)? • Trace groundwater provenance • Estimate groundwater age • Interpretation of groundwater quality • Understanding geochemical evolution (reactions and reaction rates) and recharge processes • Recognizing geochemical & biogeochemical cycles of pollutants among soil-water-atmosphere

  6. How to express isotopic compositions? • d = (Rsample-Rstd)/Rstd * 1,000 (‰) • Where R=(heavier isotope)/(lighter isotope) • Example: d18O = {(18O/16O)sample - (18O/16O)std }/ {(18O/16O)std *1,000 • See Table 1-1 on p.6 for the commonly used stable environmental isotopes

  7. Stable isotope standards and measurements • Also See Table 1-1 on p.6. • Discuss • The expression of each isotopic compositions • Standard materials for different isotopes • Preparation for the measurements (extraction methods) • Read from p.7 to p.13

  8. Isotope ratio mass spectrometry (IRMS) • See Fig. 1-4 on p.14 • Discuss • The basic instrumentation of mass spectrometer • What would be the advantage of ratio mass • How does the carrier gas He (continuous flow inlet) improve the system • What kind of interface would be possible for the smple inlet (front end) (for example Elemental analyzer or laser ablation)

  9. General Instrumentation of Mass Spectrometer (TIMS) From http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html

  10. General Instrumentation of Isotope Ratio Mass Spectrometer From http://web.sahra.arizona.edu/programs/isotopes/methods/gas.html

  11. Typical Instrumentation of Accelerator Mass Spectrometer From http://web2.ges.gla.ac.uk/~dfabel/AMS/AMS_schematic.html

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